1. Field of the Invention
This invention relates to thermal hair styling appliances, and more particularly this invention relates to thermal hair styling appliances which are versatile in that various attachments may be utilized and various heat and vapor conditions may be created.
2. Technical Considerations and Prior Art
Hair styling is an art which frequently requires various implements and environmental conditions to produce desired results. The implements assume many configurations, such as combs, brushes, cylindrical curlers, curlers with clamps, etc. Frequently, in order to increase the effectiveness of such implements, it is necessary to utilize the implements in combination with heat and/or vapor. When using heat and/or vapor, it is often desirable to have the option of varying readily both the quantity of heat and the quantity of vapor applied. The prior art does not provide an appliance having the versatility and flexibility to meet all of these requirements.
Currently on the market, there are numerous steam curling irons which have had considerable commercial success. Exemplary of these steam curling irons, is the steam curling iron disclosed in U.S. Pat. No. 3,835,292 which is assigned to the assignee of the instant invention. Although the steam curling iron disclosed in this patent performs successfully, it does not include structure for providing a range of temperatures or structure for varying the configuration of its hair styling implement. Essentially, the appliance disclosed in U.S. Pat. No. 3,835,292 provides a single implement which only allows for selective vapor application.
There are steam curling irons available, which have variable temperature control. However, the controls used with these steam curling irons have various deficiencies. One steam curling iron utilizes a low-wattage section which is not thermostatically controlled and a high-wattage section which is thermostatically controlled. With this device there is no positive cut-off for the low-wattage section, and it has been found that the stabilization temperature in the low and high-wattage sections are ultimately the same. This is because as the power is applied through the low-wattage section, the iron heats up at a relatively slow rate, but since there is no means to terminate application of power, the iron continues to heat until ultimately controlled by the thermostat on the high-wattage section. With this type of temperature control, it is extremely difficult to achieve a precise lower temperature limit.
The prior art includes another approach, in which a thermostat is utilized which includes a fixed contact and a movable contact. A temperature control knob is linked to the movable contact and mechanically changes the distance between the movable contact and the fixed contact, in order to vary the temperature at which contact will be broken. This particular approach requires a relatively sensitive and extensive mechanical linkage, which must extend between the thermostat and the control knob. Accordingly, it is difficult to juxtapose the thermostat with the heater which it monitors. In order to provide for good response and accurate control of the heater, the thermostat should be as close to the heater as possible. With this type of control, close proximity is not possible, because the temperature control knob needs to be spaced from the heater to keep the user from being burned.
A third approach, for controlling the temperature of steam curling irons, uses no thermostat at all, but rather disposes a diode between a rope heater and a power line. For low heat, the diode is switched into the circuit to reduce the power factor of the current, while for high heat the diode is switched out of the circuit, so that the heater receives all of the power. This approach is undesirable in that for temperature stabilization, the steam curling iron relies on ambient heat losses, instead of on the positive control of a thermostat. In addition, only low-wattages can be used, which lengthens the heat-up time considerably.